1. Field of the Invention
The present invention relates to a common rail fuel injection device, and in particular, to control for determining an injection pattern for injecting fuel from an injector.
The injection pattern is composed of a plurality of injection factors, such as an injection quantity, injection timing, injection duration, the number of injections, an injection interval, a common rail pressure, and the like.
2. Description of the Related Art
In conventional control for determining an injection pattern, an ECU (an engine control unit) stores an injection quantity, injection start timing, the number of injections, and the like, which correspond to the information of an engine speed and engine desired torque (hereinafter called “desired torque”), as a compatible value. Herein, the desired torque is a desired value of engine power, which is calculated from a power index desired by a driver. A common rail fuel injection device is controlled by use of the following procedure so that the foregoing map data corresponds with an operating state.
In the conventional technology, by way of example, a common rail desired pressure PFIN (target pressure) is calculated, in addition to a pre-injection quantity Qp, a pre-interval Tp, main-injection start timing Tm, a main-injection quantity Qm, an after interval Ta, and an after-injection quantity Qa, as injection factors of the injection pattern, as shown in FIG. 1A.
A conventional control unit calculates a total injection quantity Qtotal on the basis of desired torque and an engine speed NE, and then individually calculates each injection factor (Qp, Tp, Tm, Qm, Ta, Qa, and PFIN) on the basis of the total injection quantity Qtotal and the engine speed NE. A conventional procedure for obtaining an injection pattern will be described with reference to the flowchart of FIG. 8 and a block diagram of FIG. 9.
Upon entering an injection control routine for obtaining an injection pattern (start), an operating state such as an engine speed NE, the degree of opening of an accelerator, and like is read in (step J1). Then, desired torque Treq is calculated from the engine speed NE, the degree of opening of the accelerator, and the like (step J2). Next, a total injection quantity Qtotal appropriate to the current engine speed NE and the desired torque Treq is read from memory, which stores various injection factor patterns based on the engine speed NE and the desired torque Treq (step J3).
In step J3, as shown in FIG. 9, four values of the total injection quantity Qtotal close to one another are searched through a map, appropriate to the current engine speed NE and the desired torque Treq. By interpolating the searched four values of the total injection quantity Qtotal with respect to four points, the total injection quantity Qtotal suited for the current engine speed NE and the desired torque Treq is calculated.
Then, a pre-injection quantity Qp appropriate to the current engine speed NE and the total injection quantity Qtotal is read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J4).
In step J4, as shown in FIG. 9, four values of the pre-injection quantity Qp close to one another are searched through a map, appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four values of the pre-injection quantity Qp with respect to four points, the pre-injection quantity Qp suited for the current engine speed NE and the total injection quantity Qtotal is calculated.
Then, an after-injection quantity Qa appropriate to the current engine speed NE and the total injection quantity Qtotal is read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J5).
In step J5, as shown in FIG. 9, four values of the after-injection quantity Qa close to one another are searched through a map, appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four values of the after-injection quantity Qa with respect to four points, the after-injection quantity Qa suited for the current engine speed NE and the total injection quantity Qtotal is calculated.
Then, a main injection start timing Tm appropriate to the current engine speed NE and the total injection quantity Qtotal is read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J6).
In step J6, as shown in FIG. 9, four values of the main-injection start timing Tm close to one another are searched through a map, appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four values of the main injection start timing Tm with respect to four points, the main injection start timing Tm suited for the current engine speed NE and the total injection quantity Qtotal is calculated.
Then, pre-intervals Tp appropriate to the current engine speed NE and the total injection quantity Qtotal are read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J7).
In step J7, as shown in FIG. 9, the four pre-intervals Tp close to one another are searched through a map, appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four pre-intervals Tp with respect to four points, the pre-interval Tp suited for the current engine speed NE and the total injection quantity Qtotal is calculated. Then, after-intervals Ta appropriate to the current engine speed NE and the total injection quantity Qtotal are read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J8).
In step J8, as shown in FIG. 9, the four after-intervals Ta close to one another are searched through a map appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four after-intervals Ta with respect to four points, the after-interval Ta suited for the current engine speed NE and the total injection quantity Qtotal is calculated. Then, a main-injection quantity Qm appropriate to the current engine speed NE and the total injection quantity Qtotal is read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J9).
In step J9, as shown in FIG. 9, the main-injection quantity Qm may be calculated by subtracting the pre-injection quantity Qp and the after-injection quantity Qa calculated in steps J4 and J5, respectively, from the total injection quantity Qtotal calculated in step J3. Then, a common rail desired pressure PFIN appropriate to the current engine speed NE and the total injection quantity Qtotal is read from memory, which stores various injection factor patterns based on the engine speed NE and the total injection quantity Qtotal (step J10).
In step J10, as shown in FIG. 9, four values of the common rail desired pressure PFIN close to one another are searched through a map appropriate to the current engine speed NE and the total injection quantity Qtotal. By interpolating the searched four values of the common rail desired pressure PFIN with respect to four points, the common rail desired pressure PFIN suited for the current engine speed NE and the total injection quantity Qtotal is calculated.
Then, an injector is controlled on the basis of each injection factor (Qp, Tp, Tm, Qm, Ta, and Qa) calculated in each of steps J4 to J9 (step J11). Then, the discharge rate of a supply pump is controlled on the basis of the injector factor (the common rail desired pressure PFIN) calculated in step J10 and the current common rail pressure (step J12), and operation returns. Operation shown in the foregoing injection control routine is repeated injection-by-injection (refer to, for example, Japanese Patent Laid-Open Publication No. 2002-155783).
The conventional common rail fuel injection device gives excellent control ability for an engine, because the common rail fuel injection device can freely set each injection factor (injection quantity, injection timing, injection duration, the number of injections, interval, common rail pressure, and the like) of the injection pattern. In the common rail fuel injection device, optimal common rail pressure differs in accordance with the operating state of the engine. Therefore, when the operating state of the engine varies, it is necessary to make the common rail pressure follow the optimal pressure.
The pressure-rising response of the common rail pressure depends on the discharge rate of the supply pump, an amount of fuel consumption of the injector, and the like. The pressure-lowering response of the common rail pressure depends on an amount of overflow from a common rail to a fuel tank due to a pressure-reducing valve and the like, an amount of fuel consumption of the injector, and the like. Thus, there are limits to the pressure-rising response and the pressure-lowering response of the common rail pressure. Thus, delay in the response of the common rail pressure makes the injection pattern inappropriate.
An example will be described. In the case of full-throttle acceleration, it is desired to carry out injection with an injection pattern (refer to FIG. 1A) which corresponds to a common rail at high pressure. In the case of the full-throttle acceleration from idle, however, there is response delay in actual common rail pressure and hence the injection duration becomes long, as shown in FIG. 1B. Thus, since the terminal point of main injection shifts on the retarded side, emission and fuel efficiency become worse.
Japanese Patent Laid-Open Publication No. 2002-155783 mentioned above discloses a control technology for correcting injection timing in accordance with the common rail pressure. Of a plurality of the injection factors constituting the injection pattern, the invention of Japanese Patent Laid-Open Publication No. 2002-155783 can correct only the injection timing, but cannot optimize the other injection factors (injection quantity, injection duration, the number of injections, interval, common rail pressure, and the like).
In the conventional control for determining an injection pattern, as described above, each injection factor is individually determined. In each process for determining each injection factor, four values of the injection factor close to one another are searched through a map, appropriate to a current operating state. Then, the four searched values are interpolated with respect to four points, in order to calculate the injection factor suited for the current operating state of the engine. Therefore, a calculation load in the injection control, which requires high-speed calculation, becomes heavy.